The present invention relates to a battery protection circuit, particularly to a circuit that supplies necessary power to a load by starting to discharge electric power of the battery in place of a main power source when the battery is fully charged and thereafter disconnect itself from the load to be recharged in order to protect the battery from excess currents when the voltage reaches a specified level.
In a conventional method, a battery protection circuit as shown in FIG. 1, has been employed; however, since the prior art method employs a fuse FS as a protective device for batteries against excess currents, there is such an inconvenience that the fuse has to be replaced whenever it is destroyed by an excess current. To have a hysteresis as shown in FIG. 3, the conventional circuit is designed in such a way that a reference voltage Vref fed into each input port of comparators L1, L2 through Zener diodes D1, D2, and a charging current from the battery flowing into other input ports of comparators L1, L2 through a variable resistor VR1 and resistors R3, R4, R5, R6 are each compared in the comparators by way of turning-ONs and turning-OFFs of a plurality of transistors so as to satisfy the hysteresis characteristics; but, the prior art method is not only complicated in its configuration but also requires a relatively large number of parts, thus puts heavier burden on the cost factor.